1. Field of the Invention
The present invention relates to steam generators and particularly to such steam generators for use in nuclear power plants.
2. Description of the Prior Art
Steam generators for use in power plants, and particularly for use in nuclear power plants are well known, such as the type of steam generator manufactured by Westinghouse. One such typical prior art steam generator is shown in FIG. 1 of the drawings. These prior art steam generators utilized in nuclear power plants are normally contained in a containment building, such as one made of concrete. Moreover, these prior art steam generators known to applicant are unitary structures comprising a housing having an upper shell and lower shell portion with a moisture separator, including a swirl vane moisture separator, normally being located in the upper shell portion and with a tube bundle normally being located in the lower shell portion. In such prior art steam generators presently employed in nuclear power plants, the steam generator is completely enclosed and is placed in the containment building prior to the concrete being poured. As a result, once the containment building is sealed there is no way to replace this steam generator without breaking or destroying the containment building. Accordingly, if there is a failure in the tube bundle, it has heretofore been necessary to break the containment building in order to repair the steam generator as that is the only manner in which access can be had to various portions of the steam generator. Moreover, failure in the tube bundle of this prior art unitary type of steam generator has required replacement of the entire steam generator in order to allow for such repair, which complete replacement is quite costly in that such a steam generator costs approximately $15,000,000 by 1976 standards.
With the widespread acceptance and use of nuclear power plants, there have been more and more such tube failures in the tube bundles of such steam generators which have required the power plant to be shut down. This, of course, can be extremely costly inasmuch as the steam generators are a vital component in the operation of the nuclear power plant. Moreover, since such nuclear power plants normally include three or four such steam generators in operation, the cost of replacement and/or repair can become quite prohibitive.
Although the use of modular housing in various types of heat exchangers has been well known, such as disclosed in U.S. Pat. Nos. 1,372,010; 2,228,549; 2,241,209; 1,564,446; 1,790,897; 973,610; 514,338 and 784,192, such techniques, to applicant's knowledge, have not been used with respect to steam generators and particularly steam generators for use in nuclear power plants, despite the serious problems encountered with respect to repair and/or replacement of these steam generators in situ. These disavantages of the prior art are overcome by the present invention.